1. Field of the Invention
The invention relates to fluid drive processes for the recovery of hydrocarbons from hydrocarbon-containing subterranean formations. In one more specific aspect, it relates to an improvement wherein selective drive through more permeable as opposed to less permeable zones of a formation is corrected.
2. Description of the Prior Art.
Processes for the recovery of liquid hydrocarbons from a hydrocarbon-bearing subterranean formation by injection of a drive fluid through an injection well vertically traversing the formation and recovery from a production well of displaced liquid hydrocarbons are well known to those skilled in the art. Particularly, waterflooding processes of this type are well known as are waterflooding processes involving the use of surfactants and thickening polymers.
It is also well known to those skilled in the art that many formations are not adequately flooded out employing these methods because the formation is not of uniform permeability. Often, the drive fluid will channel through a highly permeable zone between an injection well and a producing well leaving much of the residual oil unaffected by the flooding procedure.
One mitigation of the problem is disclosed by U.S. Pat. No. 3,667,545 wherein the boundary zone of a lesser permeable zone adjoining a more highly permeable zone is injected between an injection and a production well with a mobility reducing agent. This procedure allows differential injection into the lesser permeable zone as opposed to the highly permeable zone, and is proposed to increase recovery by this means.
However, in spite of such developments, more effective means of carrying out more efficient flooding with drive fluids are earnestly sought after in order to increase economically recoverable reserves of hydrocarbons.